1. Field of the Invention
This invention relates generally to devices for picking up a plate or sheet of ferrous material individually from a stack of same, with a self regulating permanent magnet safety which is activated when all power to the device is withdrawn.
2. Description of the Prior Art
A common problem with known pickup devices of the vacuum and electromagnet type is that there are no built in automatic safety devices. The vacuum cup often will not seat properly to allow the cup to obtain a positive and quick vacuum lock. This is usually the case when two or more cups are used on the same device and especially on irregular surfaces.
Known vacuum cup and electromagnet combination devices do not offer variable holding power in either or both structures to allow a positive removal of one piece of ferrous metal at a time from a stack either by manual or automatic regulation. Regulated power as well as cushioning is needed to prevent distortion of the workpiece in ferrous or non-ferrous materials, especially in the transport of thin material in sizable sheet form with no means of underlayment or support.
Also, no known device has an automatic non-powered safety stand-by for ferrous materials which can retain the work pieces in the case of a complete power failure and not allow the workpiece to fall on working people in the area. The lack of a safety stand-by creates a very serious and dangerous situation to all concerned in todays' industry.
Known prior art patents which may be pertinent to this invention are as follows:
U.S. Pat. No. 1,181,112 J. P. C. Charlebois May 2, 1916,
U.S. Pat. No. 1,207,662 R. B. & H. S. Thomas et al Dec. 5, 1916,
U.S. Pat. No. 2,474,141 R. T. Chatterton June 21, 1949,
U.S. Pat. No. 3,159,418 J. J. Hanson Dec. 1, 1964,
U.S. Pat. No. 3,409,149 P. Graux Nov. 5, 1968,
U.S. Pat. No. 3,517,835 H. E. Temple June 30, 1970.
None of these known prior art devices offers the new and unique features of the invention disclosed herein.